In vehicles, it is necessary to supply and control power to various electric components. In order to collectively supply and control power to various electric components in this way, boxes such as a junction box, a joint box, and a battery box are used. Such a box is configured by integrating components such as fuses and relays, and circuit boards.
In recent years, board blocks which are installed in one box or separately equipped with a function of a box are often used. Such a board block performs substantially the same function as that of one box.
A plurality of printed circuit boards are used in the board block, and the printed circuit boards are disposed generally parallel to each other. In order to dispose the printed circuit boards in parallel, the printed circuit boards should be electrically connected by wires or jumper pins. Further, a structure for fixing the printed circuit boards should be provided separately. Thus, the board block according to the related art is relatively large and has a number of components.
Further, since connector units for electrical connections of printed circuit boards to the outside, respectively, cannot but be located at corresponding positions on a lower surface of a housing in the board block according to the related art, circuit patterns of the printed circuit boards become long. Accordingly, a voltage drop and significant amounts of heat are generated in a relatively long circuit pattern, and an entire size of the board block increases due to the large sizes of the printed circuit boards.
Meanwhile, the printed circuit boards are generally manufactured by forming circuit patterns in insulation layers which are formed of a synthetic resin. A separate insulation layer is formed to cover a circuit pattern formed on the insulation layer and a circuit pattern is formed again on a surface of the separate insulation layer. Such a printed circuit board is referred to as a multilayered printed circuit pattern. Of course, circuit patterns may be formed on opposite surfaces of one insulation layer, and a solder resist may be applied to surfaces of the circuit pattern and the insulation layer to form a printed circuit pattern.
It is impossible to bend the printed circuit board having an insulation layer formed of a synthetic resin. The reason is because the circuit pattern or the insulation layer cannot be bent by approximately 90 degrees, and if the insulation layer is bent by the degree, it is susceptible to being broken.
Further, when a printed circuit board is installed and used in a narrow space in the housing, lots of heat is generated in the printed circuit board. If the generated heat is not more effectively dispersed to the entire printed circuit board, heat emission is concentrated at a specific location, so the printed circuit board may be damaged by heat at the specific location or components installed at the location may be damaged by heat.